1. Technical Field
The present disclosure generally relates to label printers, and, more particularly, to an improved apparatus and method for automatically sensing and setting label length in a label printer.
2. Background of Related Art
Labels are everywhere in our daily life and have many uses, for example, for the identification and tracking of products in the distribution chain, identification of laboratory samples, and for document and records identification. Almost every product, such as fruits, manufactured foods, electrical or mechanical equipment, books, consumer goods, etc., includes some form of label. Such labels may include graphic images, human-readable alphanumeric text, and machine-readable barcode. Many types of label media exist, and many techniques for printing labels are used. For example, thermal transfer techniques are widely used in modern industry.
Generally, two kinds of thermal label media are commonly used. One is a tag stock (no adhesive) type. In this type, the media itself includes multiple pages attached end-to-end and wound on into a roll. This tag stock type uses an index mark, index notch, or an index hole to delineate labels from each other. This delineation feature may be used to set a starting position for printing whereby a label printer indexes the printed image from the starting position as defined, directly or indirectly, by the delineation feature of the media.
Another popular type of media is a label type which has two layers: a backing (or liner) and a self-adhesive label attached to the backing. The self-adhesive labels are detached or peeled from the backing after printing, whereupon the label may be attached to the desired item.
Each type of media may use a particular technique for separating the labels from the roll as they advance out of the printer. For this purpose, the tag stock type provides several methods. One of them is perforations on boundaries of each label or tag. The perforation method provides boundaries for each label and makes it easy for a user to cleanly tear off a label form the roll. Other methods include a manual (e.g., serrated edge) or automatic cutting mechanism (e.g., guillotine), a notch, hole, or mark for each label at a starting position for printing.
Typically, a label printer must be manually calibrated to set a label starting position when a new supply of label media is loaded into the printer. Inaccurately setting the starting position by the user can cause printing problems such as poor registration, double feeding, and so forth, and as a result, waste labels and time. Thus, accurately setting a starting position for a label printer has substantial impact on the process of printing labels.